why I have chosen/stick to this very model

I think this is may the last Thinkpad purchase I ever made, not because I don't like it, actually I love it, but I don't like these "newer ones" (ThinkPad X40 and higher).

For me this this very model was/is the (second) last perfect one, so I never got a newer one and the last known good, the X32, is not a update which is really enhancing.
My X31 is very solid, ultraportable and fast enough for the "office" stuff I do with it.

This is partly may also featured by the newer ones, but I miss some things of my X31 very much on them:

the port-layout is much better than the "newer one". I hate ports on the sides especially on the right one, and all newer ones have all ports there...

the battery in the back makes the newer ones sort of unbalanced and causes these port-layout problems

the LCD cover with this thick, wide, "salient" borders is absolutely robust and "unbreakable". Or at least feels like this ;)

the overall case feels much better engineered, like I could walk over it without doing any damage, the newer ones just don't feel like this (no I am not going to try it)

its one of the last fully IBM engineered ones

even if at first seemed like Lenovo could keep up the "legendary" quality, or even increase it to the old "pre-outsourcing" level, it now seems like this was wishful thinking